In e.g. mining, drilling or road milling applications, a drive body, which may have the form of e.g. a drum or a drill head, is provided with a number of replaceable bits, which present a very hard cutting point. Non-limiting examples of such drive bodies are shown in FIGS. 1 and 14-20 of U.S.2008/258536A1.
The bit shown in U.S.2008/258536A1 comprises a head portion, which may be approximately conical and taper towards a cutting point; and a shank, which is insertable into a bit holder. The bit is a wear part, and hence it is desirable to be able to rapidly replace worn bits, and also to produce such bits at as low cost as possible.
The bit holder is, in turn, fixedly connected to the drive body. The functions of the bit holder are to ensure that the bit is angled in the desired direction and to replaceably receive the bit. The bit holder may be integrated with the drive body, it may be formed in one piece with the drive body, or it may be attached to the drive body. The bit holder may protrude more or less from the surface of the drive body.
U.S. Pat. No. 5,261,499 discloses a drill bit, which is designed according to the principles set forth above, and where the head portion of the bit is rotatable relative to the shank, which serves to distribute wear more evenly over the head portion.
U.S. Pat. No. 3,342,531 discloses various drill bit designs, which provide strictly conical bit heads, which are attachable on a shank, which is in turn attachable to a bit holder.
U.S. 2008/0309148A1 shows a bit design according to the pre-characterizing portion of claim 1.
There is a general need for improvements in cutting bit and bitholder designs.